From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S265778AbUGBBYc (ORCPT ); Thu, 1 Jul 2004 21:24:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S265515AbUGBBYc (ORCPT ); Thu, 1 Jul 2004 21:24:32 -0400 Received: from ozlabs.org ([203.10.76.45]:45231 "EHLO ozlabs.org") by vger.kernel.org with ESMTP id S265778AbUGBBYa (ORCPT ); Thu, 1 Jul 2004 21:24:30 -0400 Date: Fri, 2 Jul 2004 11:20:12 +1000 From: David Gibson To: Oleg Nesterov Cc: linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds Subject: Re: [BUG] hugetlb MAP_PRIVATE mapping vs /dev/zero Message-ID: <20040702012012.GC5937@zax> Mail-Followup-To: David Gibson , Oleg Nesterov , linux-kernel@vger.kernel.org, Andrew Morton , Linus Torvalds References: <40E43BDE.85C5D670@tv-sign.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <40E43BDE.85C5D670@tv-sign.ru> User-Agent: Mutt/1.5.6+20040523i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 01, 2004 at 08:29:18PM +0400, Oleg Nesterov wrote: > Hello. > > Hugetlbfs mmap with MAP_PRIVATE becomes MAP_SHARED > silently, but vma->vm_flags have no VM_SHARED bit. > I think it make sense to forbid MAP_PRIVATE in > hugetlbfs_file_mmap() because it may confuse user > space applications. But the real bug is that reading > from /dev/zero into hugetlb will do: > > read_zero() > read_zero_pagealigned() > if (vma->vm_flags & VM_SHARED) > break; // OK if MAP_PRIVATE > zap_page_range(); > zeromap_page_range(); > > We can fix hugetlbfs_file_mmap() or read_zero_pagealigned() > or both. Err... surely we need to fix both, yes? -- David Gibson | For every complex problem there is a david AT gibson.dropbear.id.au | solution which is simple, neat and | wrong. http://www.ozlabs.org/people/dgibson